The present invention relates to an apparatus and a method for combining images, and more particularly, to an image combining apparatus and method thereof for combining a plurality of images partially including an overlapping region having the same image, to generate one panoramic image having a wide angle of view.
According to the conventional method of generating a panoramic image having a wide angle of view by combining a plurality of images partially having an overlapping region of the same image, two images are combined on a plane by geometrical transformation such as Affin transformation or the like to coincide coordinates values of two corresponding points, which are extracted from the overlapping regions having the same image but having different coordinates values.
However, in a case where conditions, particularly exposure conditions, of photographing the plurality of images are different for each image due to some factors of a photographing subject, even if the two images are combined precisely with the corresponding points being coincided according to the conventional method, the boundary of the images would have a conspicuous line due to the difference in lightness of the images.
The disadvantage of the conventional image combine technique is explained with reference to FIGS. 1, 2A, 2B and 3.
It is assumed herein that an image of a subject shown in FIG. 1 is picked up by an electronic still camera or the like, taking two frames (frame fl and frame f2) of photographs. Since the subject picked up by the frame fl has a dark atmosphere as a whole, the camera corrects an exposure amount at the time of image pick-up such that the dark portion would be lighter. As a result, an image shown in FIG. 2A is obtained. Since the subject picked up by the frame f2 has a light atmosphere as a whole, the camera corrects an exposure amount at the time of image pick-up such that the light portion would be darker. As a result, an image shown in FIG. 2B is obtained. Accordingly, even if the two inputted images (images in FIGS. 1A and 1B) are combined precisely, the combined image shown in FIG. 3 would have a conspicuous line due to the difference in lightness.